Insert type spinneret



H. F. HUME INSERT TYPE} SPINNERET July 8, 1969 Filed March 20, 1967 I 1L 7 3 w 4 4 2 i K 2 mi a g O 8 4 2 2 x 3 I 3 FIG-6 FIG.8

FIG-ll HAROLD FREDERICK HUME BY f/owww ATTORNEY J y 1969 H. F. HUME 3,453,689

INSERT TYPE SPINNEHET Tiled March 20'. 1967 Sheet 0'02 INVENTOR HAROLD FREDE ICK HUME ATTORNEY United States Patent 3,453,689 INSERT TYPE SPINNERET Harold Frederick Hume, Wilmington, Del., assignor to E. I. du Pont de Nemours and Company, Wilmington,

Del., a corporation of Delaware Filed Mar. 20, 1967, Ser. No. 624,460 Int. Cl. D01d /00 US. Cl. 188 5 Claims ABSTRACT OF THE DISCLOSURE A spinneret for the production of composite filaments having a shaped tubular insert positioned in the main leg of a branched passageway connecting the upper and lower surfaces of the spinneret plate.

This invention relates to spinnerets and more particularly to a spinneret for the production of composite filaments. There have been various types of spinnerets proposed for the spinning of hollow and also sheath-core filaments. The manufacture and assembly of these spinnerets require great care and precision and have the further disadvantages of complexity and high cost. Due to the precision required in their manufacture and assembly, there is a decided lack of flexibility between spinnerets in that parts cannot be readily interchanged while still maintaining uniformity in filament cross-section.

Summary of the invention One of the objects of this invention is to provide a novel and improved spinneret for the production of composite filaments that is simple and easy to manufacture and assemble. Another object of this invention is to provide a spinneret for the production of sheath-core filaments wherein the thickness of the sheath, as well as the location of core or cores within the sheath, is accurately and consistently controlled. One embodiment of the present invention contemplates a spinneret that includes a plate having top and bottom surfaces connected by a through passage having successive cylindrical, tapered and capillary lengths. A branch passage connects the top surface of the plate to the cylindrical length of the passage. A tubular insert including first, second and third cylindrical portions of successively decreasing cross-sectional dimensions is positioned in the through passage of the spinneret. The first cylindrical portion is the largest portion, having greater cross-sectional dimensions than the through passage and having a flange which engages the top surface of the plate. The second cylindrical portion is closely fitted in the through passage and extends approximately to the upper edge of the branched intersection. The third cylindrical portion of the insert which is smaller in cross-sectional dimensions than the cylindrical length of the passage projects substantially through the remainder of the cylindrical length and terminates above the tapered length.

Brief description of the drawings FIGURE 1 illustrates an exploded cross sectional view of one embodiment in accordance with the invention.

FIG. 2 is a top view of the spinneret plate of FIG. 1.

FIG. 3 is an enlarged partial view of FIG. 1 with the insert in place.

FIG. 4 is a partial top view of another embodiment of a spinneret plate according to the invention.

FIG. 5 is an enlarged partial cross sectioned view of FIG. 4 with the insert in place.

3,453,689 Patented July 8, 1969 FIGS. 6-11 show modified forms of the third cylindrical portion of the insert.

Description of the illustrated embodim'lents Referring now to FIGS. 1-3, the spinneret of this invention includes a plate 10 adapted to be mounted in a conventional filter pack (not shown) for supplying two polymer compositions A and B. Plate 10 has a top surface 14 and a bottom surface 16 connected by through passages 18, each of which includes successive concentric cylindrical, tapered and capillary lengths 20, 22 and 24, respectively. A pair of recesses 26 provided in top surface 14 are in communication with passages 18. Angularly disposed branch passages 28 connect the cylindrical length of each passage 18 with the top surface 14 between recesses 26. A plurality of inserts 12 are provided, one for each passage 18.

Each insert includes successively reduced first, second and third concentric cylindrical portions. The first cylindrical portion 30 has greater cross-sectional dimensions than those of the cylindrical length 20 of through passage 18 but somewhat smaller than recess 26 and includes a flange 32 which engages top surface 14 within recess 26. Projecting from flange 32 is a second cylindrical portion 34, the cross-sectional dimensions of which are slightly smaller than those of cylindrical length 20 to provide a snug but not a drive fit between portion 34 and cylindrical length 20. Portion 34 extends through length 20 to the upper edge 35 formed by the intersection of branch passage 28 and cylindrical length 20. Finally projecting from portion 34 is a third cylindrical portion 36 that extends beyond the lower edge 37 formed by intersection of the through and branch passages 18, 28. Cylindrical portion 36 has smaller cross-sectional dimensions than cylindrical length 20 and, being concentric with cylindrical portion 34, provides a concentric annular space 38 around portion 36. Insert 12 has an axial bore 40 therethrough.

In the melt spinning processes preferred in the practice of this invention, the spinneret plate 10 is mounted in a conventional filter pack assembly to supply two different molten polymers to the spinneret. A molten polymer A flows through bore 40 of insert 12 through tapered length 22 and capillary length 24 to form the central portion of the filament being extruded. A second molten polymer B flows into branch passage 28 into coaxial space 38 surrounding portion 36 of insert 12 and outwardly as a concentric sheath through capillary length 24. Filaments produced from this spinneret exhibit a consistent degree of uniformity with respect to thickness of the sheath as well as location of the core within the sheath. It can readily be seen that the engagement of flange 32 of insert 12 and top surface 14 of the plate 10 provides a positive seal to prevent pclymer leakage from source A between the second cylindrical portion 34 of the insert and the cylindrical length 20 of passage 18. The combination of the snug fit between cylindrical portion 34 and cylindrical length 20 and flange 32 engaging top surface 14 provides for concentric alignment of the insert in passage 18 while providing a spinneret that may be assembled and disassembled with ease. Terminating the insert slightly above the tapered length 22 of passage 18 has eliminated an alignment problem experienced with prior art insert type spinnerets wherein an extremely fine portion of the insert extends through the capillary length of the spinneret passage and is extremely difiicult to concentrically align in the capillary. The concentric spacial relationship between cylindrical portion 36 and tapered length 22 is believed to contribute significantly to filament sheath-core concentricity.

In another embodiment of the invention shown in FIGS. 4 and 5, a spinneret plate is provided which is capable of spinning filaments made up of more than two polymers. The structure is similar to that described above, the main difference being the provision of opposed angularly disposed branch passages 28' connecting the top surface 14 of plate 10 with cylindrical length of passage 18' and of a single recess 26' in surface 14' in communication with passage 18'. The opposed branch passages 28' along with axial bore 40 of insert 12 are used to feed molten polymers A, B, and C to tapered length 22' and capillary length 24' for extrusion as a composite filament. By varying the pressures applied to the molten polymers, the amounts of each composition going into each filament can be precisely controlled.

It can be readily understood that by only modifying the end of the third cylindrical portion 36 of insert 12, a wide versatility and choice of filament cross-sections can be obtained at a minimum cost, as for example, sealing the end and providing peripheral holes 42 (FIGS. 6, 7) or axial holes 44 (FIGS. 8, 9) or interconnected slots 46 (FIGS. 10, 11). Additional positioning support within passage 18 for cylindrical portion 36 of insert 12 may be provided if needed by machining lands or providing an interrupted collar on portion 36 of the insert to serve as a positioning guide in the cylindrical length 20 of passage 18.

The spinneret of this invention may be made from metals known in the art, such as stainless steel or platinum group metals, Furthermore, the insert may be formed from a material which is different from that of the spinneret. However, in most instances, it is advantageous to use the same metal to prevent unequal expansion of parts from a difference in thermal coefficients. While the tapered length of the passage is particularly advantageous in spinning filaments having circular cross-sections, a passage having only successive cylindrical and capillary lengths is generally more effective in preparing profiled filaments (such as trilobal, tetralobal, keyhole, and serrated). In some cases, it is also advantageous to generate a more complicated shape in the capillary length. However, in each case, termination of the third cylindrical portion of the insert above the capillary length of the through passage improves the concentricity of the sheath with respect to the core of extruded filaments over prior art spinnerets.

The invention is preferably used in the melt spinning of polymers such as polyesters, polyamides, polyolefins, polyacetals and polycarbonates. However, the spinneret may also be used for the spinning of filaments composed in whole or in part of cellulosic fiber-forming materials or synthetic addition polymers such as acrylonitrile polymers either by wet or dry spinning. It is obvious that gas, preferably inert, may be substituted for polymer A to yield hollow or multi-channel cross sections. It is also obvious that the invention can be used in the production of filaments having cross-sections whose outer surface has other than a circular cross-section (i.e., trilobal, tetralobal, serrated) as well as shaped core or core elements. For example, it is possible to introduce a round cross section core into a trilobal sheath. Moreover, if desired, each filament of the bundle issuing from the spinneret can have a different and yet carefully controlled internal and external cross section. Further, since the inserts 12 are easily interchanged, a spinneret can rapidly be converted from one type-product to another type of product by just changing the inserts.

The spinneret of this invention has the advantage of being simple in construction, providing for wide versatility at a minimum investment, accurately controlling the thickness of the sheath as well as the location of the core within the sheath in a sheath-core filament and is easily maintained.

It is to be understood that the embodiments disclosed may be altered and numerous other embodiments can be contemplated without departing from the spirit and scope of the appended claims.

What is claimed is:

1. A spinneret for the production of composite sheathcore filaments comprising:

(a) a plate having top and bottom surfaces connected by at least one through passage, said through passage having successive cylindrical, tapered, and capillary lengths, said plate having an angularly disposed branch passage connecting said top surface and said cylindrical length above the juncture of the cylindrical and tapered lengths; and

(b) an insert positioned in said through passage, said insert having successively reduced first, second and third cylindrical portions, said insert having an axial bore therethrough, said first portion having greater cross-sectional dimensions than the through passage and having a flange engaging said top surface, said second portion projecting from said flange into said cylindrical length proximal to the branch passage connection therewith, and being substantially the same cross-sectional dimensions as the cylindrical length, said third portion extending beyond said branch passage substantially to said tapered length, said axial bore and said branch passage being in communication with separate polymer sources whereby to supply polymers to the sheath and core of a filament formed by extrusion through said capillary length.

2. The spinneret of claim 1 wherein said top surface is provided with at least one recess, said through passage being in communication with said recess, said first cylindrical portion being contained therein.

3. A spinneret for the production of composite sheathcore filaments comprising:

(a) a plate having top and bottom surfaces connected by at least one through passage, said through passage having sucessive concentric cylindrical tapered and capillary lengths, said plate having a recess in said top surface in communication with said through passage, said plate having an angularly disposed branch passage connecting said top surface and said cylindrical length, said branch passage intersecting said cylindrical length forming an upper and lower edge; and

(b) an insert having successively reduced concentric first, second and third cylindrical portions, and insert having an axial bore therethrough, said first cylindrical portion being contained in said recess, said second cylindrical portion extending to said upper edge and being substantially the same crosssectional dimensions as the cylindrical length, said third cylindrical portion extending beyond said lower edge and terminating above said tapered length.

4. A spinneret for the production of composite filaments comprising:

(a) a plate having top and bottom surfaces connected by at least one through passage, said through passage having successive cylindrical, tapered and capillary lengths, said plate having opposed angularly disposed branch passages connecting said top surface and said cylindrical length; and

(b) an insert fitted into said through passage, said insert having successively reduced first, second and third cylindrical portions, said insert having an axial bore therethrough, said first portion having greater cross sectional dimensions than the through passage and having a flange engaging said top surface, said second portion projecting from said flange into said cylindrical length proximal to the branch passages connections therewith and being substantially the same cross sectional dimensions as the cylindrical length, said third portion extending substantially to said tapered length, said axial bore and each of said branch passages being in communication with sep- References Cited anate polymer sources whereby to supply polymers to a composite filament formed by extrusion through FOREIGN PATENTS said capillary length. 270,772 8/1964 Australia.

5. The spinneret of claim 4 wherein said top surface is 5 1,102,339 3/1961 Germany.

provided with a recess, said through passage being in 1,061,692 3/ 1967 Great Britaincommunication with said recess, said first cylindrical portion being contained therein. WILLIAM J. STEPHENSON, Primary Examiner. 

